1. Field of the Invention
This invention relates to an improved pyroelectric detector as part of a nonlinear dynamic system with a higher effective amplification whereby random incoming infra-red radiation is converted into electrical signals. The invention uses the effect that nonlinear dynamic systems near their bifurcation point can act to amplify small signals. Thus, it is possible to develop practical infra-red sensor applications.
The invention uses the well known applications of pyroelectric detectors. In pyroelectric materials, relatively small temperature changes cause high electric fields. The present invention converts the temperature change into an electric signal in a nonlinear dynamic system, and amplifies that signal in the same nonlinear system.
2. The Prior Art
Conventional pyroelectric detectors make use of ferroelectrics, which first have to be polarized for that application. One of the best materials used in pyroelectric detectors is modified triglycine sulphate (TGS). These modifications are specially doped TGS-crystals (e.g. L-alanine-doped or deuterated) to stabilize a high internal bias field and to increase the sensitivity of the material.
Furthermore, it is well-known, that a series-resonance circuit with ferroelectric TGS capacitor can exhibit different kinds of bifurcations (symmetry-breaking and period-doubling bifurcations) according to the theory of nonlinear dynamic systems. The bifurcations may be observed, if the external parameters of the circuit (amplitude and frequency of the driving voltage and temperature of the ferroelectric capacitor) are suitably chosen. The amplitude of the driving voltage is in the order of magnitude of the coercive field strength of the ferroelectric in these cases.